The present invention relates to a hydraulic power transmission system having one or more hydraulic circuits for distributing or apportioning hydraulic power in addition to any existing power circuits.
1. Field of The Invention
This invention relates to a hydraulic power transmission system for use in material handling machinery such as a hydraulic power shovel. The invention utilizes a motor-pump unit to create an auxiliary hydraulic power circuit in addition to any existing power circuits. The motor of the unit is run by the fluid from one of the existing power circuits and operates to drive the pump of the unit. The pump feeds fluid to a second power line which is a part of an auxiliary hydraulic power circuit.
2. Description Of The Prior Art
In the United Kingdom Pat. No. 1,128,657, published on Oct. 2, 1968, with a priority filing date of Sept. 30, 1964 based on a German patent application No. G41650ic/59a, there is taught a hydraulic power transmission system such as is shown in FIG. 1 of the attached drawing. FIG. 1 illustrates diagrammatically the general arrangement of a motor M which drives a plurality of hydraulic variable delivery pumps P1, P2. Each pump supplies hydraulic fluid to its respective hydraulic power line L1, L2 leading to respective distributing units B1, B2. A regulator R is provided for simultaneously changing the outputs of the pair of pumps P1 and P2 as a function of the sum of the pressures prevailing in both circuits, whereby the sum of the powers absorbed by each line remains constant. With this arrangement, it is obviously difficult to operate simultaneously and in a completely independent manner a plurality of load circuits from the same distributing unit. Consequently the total power available cannot be properly distributed among the various receivers. This is observed notably in hydraulic power shovels, comprising for example a unit B1 for distributing pressure fluid to the boom luffing motion, operating the bucket and the left-hand translation motor, and another unit B2 for distributing pressure fluid to the bucket arm control motion, the right-hand translation motor and the turret slewing mechanism. In this case, only two simultaneous working movements are permitted, namely one movement for each pump P1, P2, for any increment in the number of pumps would reduce considerably the power available for each movement.
It is the primary object of the present invention to avoid these inconveniences by improving the versatility of a hydraulic circuit of known type and therefore increasing the working capacity of a machine equipped to such circuit.